Solvent refining of hydrocarbon oil



April 28, 1936. R. E, MANLEY 2,038,798

SOLVENT REFNING OF HYDROCARBN OIL Filed Maron 7, 1932 7 /YIHTEA lffl/775,?

INVENTOR TTORNEY lfl Patented Apr. 28, 1.936

UNITED STATES 2,038,798 SOLVENT REFININgnEF HYDROARBON 4Robert E.Manley, Beacon, N. Y., assignor to The Texas Company, New of DelawareApplication March 7,

8 Claims.

'Ihis invention relates to reflning hydrocarbon oils by solventextraction and to an improved process for carrying out the extraction.

The invention contemplates a continuous countercurrent process forextracting hydrocarbon oils, such as lubricating oils, kerosenes,naphtha fractions and the like, with a selective solvent liquid such asfurfural, or a derivative thereof, for the removal of undesiredconstituents wherein the solvent is continuously recovered from theseparated hydrocarbon fractions and recycled through the system 'fortreating fresh oil. The invention is particularly adapted to thetreatment of lubricating oil fractions derived from asphaltic,ymixed-base or parain-base 'crude sources wherein it is desired toseparate therefrom fractions of relatively high viscosity index whichmay be subsequently nished up by acid treatment and clay contacting toproduce a superior lubricating oil product.

More specically, my invention comprises continuously andcountercurrently contacting hydrocarbon oil, such as a lubricating oilfraction, with furfural, forming a liquid portion comprising relativelyhigh viscosity index oil and some dissolved solvent liquid, and anotherliquid portion comprising the major part of the solvent liquid togetherwith dissolved hydrocarbons of relatively low viscosity index. 'Iheresulting llquid portions are separately treated with water which. ismiscible with the furfural under the influence of heat and thus adaptedto displace the dissolved oil therefrom. The displaced oil constituentsmay then be withdrawn and the remaining mixture of furfural and watersubjected to cooling in order to separate the water and recover thefurfural for treating fresh oil.

While in some instances the separated oil fraction, comprising therelatively high viscosity in'- 40 dex constituents, may be'nished up bycontacting with a solid adsorbent material, it is advantageous tosubject the 'separated oil to treatment with mineral acid, therebyproducing a product I lnw in sulphur and carbon residue content andsubstantiallyfree from oxidizable bodies which otherwise renderlubricating oil products unstable during their use, particularly wherethey are subjected to relatively high working temperatures.

I have found that treatment of the oil with furfural rendersl the oilmore susceptible to im- York, N. Y., a corporation 1932, Serial No.597,141

product containing much less carbon residue and sulphur than that of aproduct obtained from a similar source when treating with acid aloneaccording to the usual practice. It seems that the furfural and acideach remove materials not readily attacked by the' acid alone, or by thefurfural alone, and therefore the combination of the two steps is ofdecided advantage in producing a product of superior quality.`

It is believed that furfural exerts a solvent action upon thenaphthenic-type bodies of the oil, or those constituents which arecharacterized by their steep viscosity temperature relationship. Thus,by extraction with furfural, the undesirable constituents of relativelylow viscosity index may be removed, thereby producing a product ofrelatively high viscosity index or, in other words, having a lowviscosity temperature susceptibility. The viscosity index hereinreferred to may be determined by the method of Dean and Davis publishedon pages 618-619 of the 1929 issue of Chemical and MetallurgicalEngineering.

Mineral oil has, in the past, been treated with liquid sulphur dioxidefor the purpose of removing certain unsaturated constituents includingnaphthenic bodies. However, liquid sulphur di-l oxide exerts a selectivesolvent action upon the various constituents of the oil only atrelatively low temperatures, usually in the neighborhood of 0 F.,'or, inany case, Well below 32 F.

Furfural, on the other hand, exerts a selective solvent action attemperatures well abovev 32 F. and, in fact, exerts a solvent actionupon the naphthenic-type bodies, for example, at tempera- 35 tures up to200 F. and above, and at elevated temperaturesthere is substantially nosolvent action upon the high viscosity index constituents, as would bethe case with liquid sulphur dioxide. Extraction of the oil withfurfural may, therefore, be carried out without chilling vthe oil,thereby avoiding the necessity of employing refrigeration; nor is itnecessary to employ pressures above atmospheric as in the case ofsulphur dioxide ln order to maintain it in the liquid phase.

Furfural is of particular advantage in rening wax-bearing oils derivedfrom parafiln or mixedbase crude sources and from which the waxconstituents separate as solid hydrocarbons when the oil is cooled to atemperature of '75 F. or low- 50 er. The use of liquid sulphur dioxideis precluded in treating oil of this nature, since the tempcrature atwhich the sulphur dioxide exerts a selective solvent action is wellbelow the congelation point of such oil.

reference will| now be made to the accompanying ow diagram, forming apart of this specication, which illustrates the method of treatinghydrocarbon lubricating oil fractions with furfural.

I may start out, for example, with-a lubricating oil fraction derivedfrom an asphaltic or naphthene-base crude source, such as a lubricatingdistillate derived from Columbia crude, which has the followingcharacteristics:

Gravity A. P. I

19.1 Per cent carbon residue .26 Per cent su1phur .32 Saybolt universalviscosity:

At 100 F 645 At 210 F 57 Viscosity index l 10 'I'his oil is withdrawnfrom a storage tank I and is passed through a heater 2 wherein it may beheated to'a temperature of 4from about 125 F. to about 200 F. The heatedoil is then introduced to a mixing chamber 3 wherein it is brought intointimate contact with furfural partially saturatmixing chamber 3, andwherein stratication occurs. Thus, at all times within the settlingchamber 4, there exist three strata; the middle stratum comprisingseparating liquids, the upper stratum consisting of separated oil ofrelatively high viscosity index and a small amount of solvent in theoil, and the bottom stratum consisting of extracted bodies includingthose of relatively low viscosity index dissolved in a relatively largeamount of solvent.

The upper stratum or layer is continuously decanted and conducted to thebottom of a suc- ',scribed. The furfural, substantially completelyvceeding mixing chamber 5. Fresh furfural is introduced to the upperportion of this mixlng chamber wherein itis brought intointimate contactwith partially-treated -oil being received from the settling chamber 4.

The mixture4 of oil and furfural is continuously withdrawn from themiddle portion of the mixing chamber 5 and conducted to the middleportion of the settling chamber 6 wherein stratication occurs ina'manner similar to that in the settling chamber 4. The vseparated oiland associated solvent which may` be referred to as the raflinate phaseis withdrawn from the upper portion of this settling chamber forrecovery therefrom, of the solvent while the bottom layer comprising thebulk of the solvent together with disfresh oil entering the system asalready desaturated with extracted material, is withdrawn from thebottom of the settling chamber 4-and subjected to further treatment forthe recovery of the solvent,v in a manner similar to that of the treatedoil portion mentioned above and which will nowbe described in detail.

The treated oil containing a small amount vci? :In order to more clearlydescribe the invention,

extract phase material consisting of furfural and extract oilconstituents dissolved in thesolvent, as removed from the top of thesettling chamber 6, is conducted to a heater 'I wherein it is admixedwith water and heated, under a pressure of about thirty or forty pounds,to a temperature of around 275 F. and then introduced to a settlingchamber 8.

At temperatures around 200 F. water becomes fairly miscible withfurfural and .becomes completely miscible therewith at about 275 F. sothat the oilis displaced from the solution. This separation occurs inthe settling chamber 8, the displaced oil accumulating as an upperlayer, while the mixture of furfural and water collects in the bottom ofthe settling chamber. The separated oil is then withdrawn from the topof the settling chamber 8 into'a receiver 9, and may contain smallamounts of solvent which can be removed by distillation or duringsubsequent treating.

As above indicated, the railinate phase retains some of the furfuralwhich has dissolved therein, some of the extract oilconstituents ornon-paraiilnic bodies. Upon removal of theextraction solvent either bywater displacement or by distillation these extract oil constituents ornonparaiiinic bodies remain in the raflinate. oil as impurities. Theyare not removed with the furfural during the displacement with waterbecause of their insolubility in water and they are also not removed bydistillation because they boil within the range of the constituentscomprising the raf- 'ilnate oil. These remaining impurities aretherefore removed along with any remaining solvent f` between the waterand the furfural. The water 4 is'withdrawn from the upper portion of thesettling chamber II and returned to the inlet of the heater 1, whereinit is' admixed with a fresh incoming stream of treated oil and furfural.

In a similar manner vthe solution of extracted matter and furfural isconducted to a heater I2 wherein it is admixed with water and heated toa temperature of around 275 F., following which it is introduced to asettling chamber I 3. From this separating vessel, the extractedvmaterial separated from the solvent by the water is withdrawn from theupper portion of the vessel .to a receiver I4. The hot mixture offurfural and water is withdrawn frcm the bottom of the chamber I3through a cooler I5 to a final settling chamber I6. The Water separatedfrom the furfural vin this Achamber is withdrawn therefrom andconductedback to the inlet of the heater I2.

y The recovered furfural, substantially free from water and oil,collecting in the bottom of the settling chambers I I and I6 iswithdrawn therefrom and returned to the upper portion of the mixingvchamber 5 wherein it is contacted with partiallytreated oil as alreadydescribed.

While only two pairs of mixing and settling chambers have been shown inwhich the oil is brought into countercurrentvcontact with the furfural,itis contemplated that anyI number of these chambers may be employed.Furthermore, it is desirable to employ a closed systemy to permitcarrying on the process under suflicient pressure to preventvaporization of any of the liquids or materials entering into theprocess.

The solvent treated or separated oil collecting in the receiver 9 andthe extract collecting in the receiver i4 will each have the followingtests:

The above separated oil is then subjected to treatment with sulphuricacid. When treating it with twenty pounds of 98% acid per barrel of oil,and then contacting the acid-treated oil with acid-treated clay in theproportion of twenty` pounds of clay to the barrel and at a temperatureof 450 F., the product will have the tests tabulated below. For thepurpose of comparison, parallel tests are also submitted on a productobtained by subjecting a sample of similar original lubricating oilfraction to similar acid treatment and clay contacting but without theintermediate furfural treatment.

It is seen, therefore, that the acid and claytreated furfural extractedoil has a viscosity inde x of 46 'with a carbon residue of .05, ascompared with a viscosity index of l1 and a carbon residue of .15,.inthe case of a product which has not been subjected to previousextraction with furfural.

While the treatment of lubricating oil fractions derived from anasphalt-base'source has been described in the foregoing example, theinvention is not restricted to the treatment of this type and isequally'well adapted to treating paraflin-base type oils as well asvarious mineral oil fractions.

Thus, the following example illustrates the resuits obtained whensubjecting a parain distillate fraction to extraction with furfuralfollowed by treatment with sulphuric acid. A dewaxed parailn distillatefraction was subjected to countercurrent treatment at 200 F. 'withfurfural in the ratio of two parts of furfural to one part of oil.

The tests on the oil, before and after treatment with furfural, were asfollows:

` 'rr-1e solvent-refined ou was then treated with five pounds per barrelof 98% sulphuric acid, resulting in an acid-treating loss of about 5% byvolume. The acid-treated oil was then contactiiltered with twenty poundsper barrel of acidtreated clay to produce a decolorized andneutralproduct. 'I'he tests on the resulting acid-treated oil are submittedbelow together with comparative tests on a fraction obtained bysubjecting a sam ple of similar original distillate to heavy acidtreatment followed by neutralization with clay but without theintermediate solvent treatment:

Combined solvent and Acid treatacid treatment only ment Gravity A. P. I26. 4 23. 9 Percent carbon residue 16 44 Percent sulphur 25 44 Sayboltuniversal viscosi At 100 F 675 898 At 210 F 70 75 Viscosity index 87 70'Ihis example demonstrates that the same marked improvement results whentreating paraiiin-base oil in accordance with the method of myinvention.

` The acid-treated clay employed in the foregoing examples was of thetype disclosed in Chappell et al. Patent No. 1,642,871, and which hascommonly been employed in recent years in decolorizing petroleum oils.While this type of adsorbent material is preferred, obviously otheradsorbent materials may be employed, such, for example, as clays of thetype of fullers earth.

'I'he method of my invention is particularly well adapted to the reningof naphtha or kerosene fractions with furfural, and from which treated`fractions the furfural may be recovered vby water displacement as abovedescribed.

Also the invention is not limited to any particular s et of operatingconditions since the temperatures, or the proportion of solvent to oilundergoing treatment, may be varied at will, depending on thecharacteristics of the desired final product.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore, only such limitations should beimposed' as are indicated in the appended claims.

I claim:

1. The continuous process of refining a mineral lubricating oil fractionwith furfural to produce lubricating oil of high viscosity index whichcomprisesconducting the oil through a plurality of mixing and separatingzones arranged in alternate succession, conducting a. body of furfuraltherethrough countercurrently to the oil, alternately mixing togetherand then separating the countercurrently-iiowing bodies of oil andfurfural, the relatively saturated furfural coming into contact withrelatively fresh oil, whilethe relatively finished oil comes intocontact' with fresh furfural, maintaining the bodies of oil and furfuralat a temperature of about 200 F., form.

' those obtained by treating the oil with either 'the 'resultingmixtures while maintained in a 'heated condition to effect straticationand sepa- -ration of the displaced oil constituents, removing thejseparated reilned oil and the separated extracted matter, cooling theremaining mixtures of Water and furfurai to about 80 F. to effectseparation of the water, returning the separated water for treatingfurther solvent and dissolved oil, and returning the recovered furfuralfor extracting fresh oil.

v2. The process of manufacturing relatively high viscosity indexlubricating oil low in sulphur and carbon residue content fromlubricating oil fractions derived from Gulf Coastal crudes ,and the likewhich comprises counter-currently extracting the fraction with furfuralat a temperature oi from 125 to about 200 F. to remove undesirableconstituents including those characterized by low viscosity index,treating the solvent-extracted oil with a small amount of strongsulphuric acid to further removevundesirable constituents includingsulphur and carbon-forming bodies, and contacting the acid-treated oilwith solid adsorbent material to produce a neutral oil of good color.

3. The process of manufacturing relatively high viscosity indexlubricating oil low in sulphur and carbon residue content fromlubricating oil fractions derived from Gulf Coastal crudes and the likewhich comprise continuously and countercurrently extracting the fractionwith furfural at a temperature of from 125 F. to about 200 F. the'rebyforming a. body of extracted oil containing some dissolved furfural,heating this body of liquid in the presence of water to a temperature ofabout 275 F. to displace the oil from the solvent, returningtheseparated solvent for mixing with fresh oil, treating the resultingoil with sulphuric acid, and contacting the acid- 'L treated oilwithsolid adsorbent material to produce a neutral oil of good color.

4. The process of preparing lubricating oil of relatively high viscosityindex from mineral lubricating oil comprising treating the oil withfurfural to extract the bulk of the undesired constituents and increasethe susceptibility of the oil .to further refining with mineral acid,subject-v ing the furfural-refined oil to treatment with a small amountof strong sulphuric acid wherehy a product is produced having qualitiesincluding viscosity index characteristics superior to the solvent oracid alone, and thereafter neutralizing the acid-treated oil.

5. The process of preparing lubricating oil of relatively high viscosityindex from mineral lubricating oil comprising treating the oil withfurabsence iural to extract the bulk of the undesired constituents andincrease the susceptibility of the oil to further reilning withsulphuric acid, subjecting the furfural-reflned oil to treatment with asmall amount of strong sulphuric acid whereby a product isproducedvhaving qualities including viscosity index characteristicssuperior to those obtained by treating the oil with either the solventor acid alone, and contacting the acid-treated oil with a solidadsorbent material to prduce a neutral oil of good color. .Y

6. In the manufacture of a nishedlubricating oil of low'carbonvresiduecontent` and high viscosity index from mineral lubricating oil stock,

the process comprising mixing vthe stock with` furfural, separating themixture into an extract phase containing relatively non-parainic oil oflow viscosity index dissolved in the solvent and a ramnate phasecomprising paraiiinic il of high viscosity index and retaining some ofthe extract phase, separating the two phases, removing the solvent fromthe rafiinate phase and removing extract phase material 'remaining inthe raf'- iinate oil by treatment with about 98% sulphuric acid in theproportion of about 5 to 20 pounds of acid perbarrel of oil. p A f 7. Inthe manufacture of a inished lubricating oil of low carbon residuecontent and high viscosity index from mineral lubricating oil stock, theprocess comprising mixing the stock with furfural, separating themixture into an extract phase containing relatively non-paramnic oil` oflow viscosity index dissolved in the solvent and a raiinate phasecomprising paraiiinic oil of high viscosity index and retaining some ofthe extract phase, separating the two phases, removing extract phasematerial remaining in the rainate oil by treatment with about 98%sulphuric acid in the proportion of about 5 to 20 pounds of acid perbarrel of cil and nally contacting the acid treated oil with a solidadsorbent material to produce a. neutral oil of good color and lowcarbon residue content.

8. The process for preparing a lubricating oil of improved viscosityindex from a viscous mini eral lubricating oil ,distillate containingnaphthenic and paraillnic hydrocarbons, and of the type derived fromMid-Continent crude, which comprises extracting the oil Witha solventcontaining furiural and thereby separating the highly naphtheniccompounds from the parainic compounds, and then treating the highlyparafflnic fraction with strong sulphuric acid Vin vthe proportion ofabout 5 pounds of Vacid per barrel of oil.

ROBERT E. MANLEY.

